Inversion and eversion ankle injuries are common in all athletic endeavors. Eversion ankle joint injuries account for ten percent (10%) of ankle injuries and inversion ankle injuries occur ninety percent (90%) of the time. These injuries are a result of the ankle joint or subtalar joint being forced beyond their normal ranges (arcs) of motion causing a tearing or stretching of the lateral collateral talo fibular and/or calcaneo-fibular ligaments. In extreme cases of force and trauma, avulsion of the lateral malleolus and oblique or vertical fractures of the medial malleolus may result. These injuries may happen from the athlete stopping abruptly while cutting laterally, or by his/her stepping with the medial side of the foot on a player's foot or ball. Once these ligaments have been stretched these injuries can and do become chronic in nature.
Present ankle orthoses and shoes or both in conjunction have not proven to be effective in preventing or treating these injuries while at the same time not unduly restricting normal motions of the athlete's foot. Acceptable treatment methods and ankle orthosis designs include taping, lace up ankle supports with steel or plastic stays, or "figure eight" straps, air casts which are medial and lateral support structures hinged at the ankle or not, and heel wedges. These known attempts are not completely satisfactory in that they unduly limit normal motion of the foot and/or are not highly effective in preventing or treating these injuries. There is a need for an improved shoe, ankle orthosis and method for protecting the ankle which overcome the drawbacks and limitations of the prior art to prevent or treat these injuries while allowing normal motion of the foot.
The efficiency of treatment utilizing known orthoses and shoes is hindered by the fact that the shoes and braces are not attached to one another and the foot can slip or slide to the lateral side of the shoe's foot bed and in extreme cases can slide off the entire foot bed. The sole can turn over (medial side raises while lateral side is weight bearing). This lateral movement of the foot and lack of lateral support from the shoe causes the sole of the shoe to move medially in relationship to the foot. This medial migration (movement) of the shoe sole causes the weight line of the shoe to shift medial of the ankle joint or subtalar joint's axis of rotation. The movement creates uncontrollable and unacceptable inversion torque which causes inversion injuries to the ankle. Another problem with present shoe and orthosis designs is that the tensioning of vertically positioned straps collapses circumferential ankle straps which slide down the ankle in time. As a result, the vertically positioned straps lose their ability to support the lateral structures of the ankle.
An object of the present invention is to provide an improved shoe, orthosis and method for protecting the ankle which avoid the aforementioned drawbacks and limitations of conventional shoes, orthoses and methods. More particularly, an object of the invention is to provide an improved athletic shoe, orthosis and method for protecting the ankle which on one hand will not impede normal ranges of motion in the ankle and subtalar joints which are necessary to walk, run or jump, while on the other hand will protect the ankle against injury.
These and other objects are attained by the improved shoe of the present invention which comprises a mid- or high-top upper, a heel-sole and means for securing the shoe on a person's foot, and wherein a heel-sole counter is provided. The heel-sole counter has a semi-rigid, shape-retaining character and includes a first portion adapted to be secured about the lower leg, a second portion spaced from the first portion and adapted to be secured about the heel and at least a portion of the foot forward of the subtalar joint for limiting subtalar joint motion by controlling the motions of segments of the subtalar joint fore and aft of the subtalar joint while permitting motion of the foot about the ankle joint, and an upwardly extending portion extending between the first and second portions for limiting torsional movement of the second portion about a longitudinal axis of the subtalar joint, as seen in a top plan view thereof, when the shoe is secured on the foot. In a disclosed embodiment, the heel-sole counter and shoe limit motion of the subtalar joint to within a normal range of motion of the subtalar joint. More specifically, supination of the subtalar joint beyond this normal range is prevented to eliminate or reduce inversion ankle injury.
For this purpose, the upwardly extending portion of the heel-sole counter of a disclosed embodiment includes a torsion bar which, as seen in transverse plan view thereof adjacent the second portion of the heel-sole counter, is elongated and relatively rigid against bending in a direction orthogonal or nearly orthogonal to the longitudinal axis of the subtalar joint as seen in a top plan view thereof while the torsion bar is narrower and more flexible in bending in another direction transverse to the direction of elongation. A further feature of the disclosed embodiment is that the torsion bar is progressively twisted along its length between the first and second portions of the heel-sole counter so that the aforementioned another direction is more forwardly facing adjacent the first portion to permit the foot to move about the ankle joint while effectively limiting motion of the second portion about the longitudinal axis of the subtalar joint.
The second portion of the heel-sole counter in the preferred embodiment extends forward of the subtalar joint on the lateral side of the foot to at least the cuboid tarsal of the foot and atop a lateral portion of the foot above the cuboid tarsal for limiting motion of the midtarsal joint and the subtalar joint of the foot. The means for securing is vertically supported by the heel-sole counter when the shoe is secured on the foot for avoiding collapse and loss of tension in the means for securing.
The first portion of the heel-sole counter is secured about the lower leg by the means for securing for yieldably resisting rotation of the tibia and fibula in a plane transverse to a longitudinal axis of the leg. The heel-sole counter in a disclosed embodiment has a construction which allows free dorsiflexion of the foot and plantarflexion with resistance. According to a further feature of the invention, the heel-sole counter in one form of the invention is configured to position the foot in the shoe in slight dorsiflexion such that when the foot plantarflexes it creates tension on the heel-sole counter for assisting the foot upon its return to its starting position.
The first portion, second portion and upwardly extending portion of the heel-sole counter are formed integrally with one another in one form of the invention. For example, the entire heel-sole counter can be formed of plastic by molding. In another form of the invention the heel-sole counter is formed of a plurality of segments such as a mid-sole member and a heel counter which are employed in combination in the shoe as the heel-sole counter.
The heel-sole counter is preferably formed integrally with a side wall of the upper and the heel-sole of the shoe during manufacture. Alternatively, the heel-sole counter can be a separate orthosis which is used inside of the shoe in combination with the shoe wherein means are provided for connecting the shoe and heel-sole counter to one another at least when secured on the foot.
A further embodiment of the shoe of the present invention employs a heel-sole counter which includes a sole extension in the shape of a single leaf spring which is capable of storing energy when deflected to provide assistance during the stance phase heel-off portion of gait, running and jumping activities for improving athletic performance. Where the heel-sole counter is integrated in the shoe, the sole extension is flattened in fabrication of the shoe to pre-load the spring.
The means for securing the shoe on a person's foot in the disclosed, preferred embodiment of the invention includes an external strap which is non-stretchable in length and which can be tensioned over the anterior aspect of the ankle between points of the shoe on or about the lateral heel-sole of the shoe and the medial anterior aspect of the ankle. The external strap is free floating intermediate its ends. Its two ends are connected to the shoe at respective points on or about the lateral heel-sole of the shoe fore and aft of the axis of the ankle joint as seen in a top plan view of the foot. The free floating intermediate portion of the strap is secured on the medial anterior aspect of the ankle by means of a free floating loop and a second adjustable strap connected thereto on the medial side of the shoe for adjustably tensioning the free floating strap. The use of this strap arrangement together with other features of the invention prevents shoe rollover.
An ankle orthosis according to the invention comprises a heel-sole counter having a semi-rigid, shape-retaining character and means for securing the heel-sole counter about the leg and foot of a user. As in the case with the aforementioned shoe of the present invention, the heel-sole counter preferably comprises a first portion adapted to be secured about the lower leg, a second portion spaced from the first portion and adapted to be secured about the heel and at least a portion of the foot forward of the subtalar joint for limiting subtalar joint motion by controlling the motion of segments of the subtalar joint fore and aft of the subtalar joint while permitting motion of the foot about the ankle joint. The first and second portions of the heel-sole counter of the orthosis are connected to one another in spaced relation by an upwardly extending portion of the heel-sole counter for securing the second portion against torsional movement about the longitudinal axis of the subtalar joint, as seen in a top plan view thereof, when the orthosis is secured on the foot and leg.
The upwardly extending portion of the heel-sole counter in a disclosed orthosis includes a torsion bar which in one form of the invention is asymmetrically positioned with respect to a longitudinal axis of the foot as seen in a top view thereof when the orthosis is in use such that torsional forces on the second portion of the heel-sole counter about the longitudinal axis of the subtalar joint, as seen in a top plan view thereof, are effectively resisted to prevent shoe rollover and inversion while the counter can flex to permit the foot to move about the ankle joint. The means for securing the heel-sole counter about the leg and foot of a user in a disclosed embodiment of the orthosis comprises two layers of material within which the heel-sole counter is sandwiched and means for securely connecting the layers and the heel-sole counter therebetween to one another and about the leg and foot of a user.
The method of protecting a person's ankle of the invention, as seen from the above description of the shoe and orthosis of the invention taken with the following detailed description of disclosed embodiments, comprises limiting subtalar joint motion of the ankle by controlling the motions of segments of the subtalar joint fore and aft of the subtalar joint while permitting motion of the foot about the ankle joint. The controlling includes providing a supporting structure about the heel and at least a portion of the foot forward of the subtalar joint for controlling the motions of segments of the subtalar joint fore and aft of the subtalar joint, and securing the supporting structure to limit torsional movement thereof about a longitudinal axis of the subtalar joint, as seen in a top plan view thereof, by an upwardly extending portion of the supporting structure secured to the lower leg. Preferably, the motion of the subtalar joint is limited by the controlling to within a normal range of motion of the subtalar joint, especially in supination of the subtalar joint. The motion of the subtalar joint is triplanar in nature and according to the invention this motion is limited in all three planes, that is, in the frontal, sagittal and transverse (cross-section of the foot) reference planes of the foot by the controlling according to the invention. The segments of the subtalar joint whose motion is controlled in closed chain subtalar joint movement during supination, for example, include limiting the inversion of the calcaneus aft of the subtalar joint and the abduction and dorsiflexion of the anterior aspect of the talus and the lateral shifting of the anterior aspect of the calcaneus fore of the subtalar joint. Preferably, this control is facilitated by also limiting the lateral shifting of the midtarsal joint at the cuboid tarsal of the foot which tends to occur in closed kinetic chain supination of the subtalar joint.
Further, according to the method of the invention, the upwardly extending portion of the supporting structure is secured to the lower leg in a manner to yieldably resist rotation of the tibia in a plane transverse to a longitudinal axis of the leg. Subtalar joint motion in the closed chain is linked with motions at other lower extremity joints including such rotation of the tibia. Relative external rotation of the tibia, for example, occurs with subtalar joint supination. Thus, control is enhanced according to the invention by employing the upwardly extending portion to both limit torsional movement of the supporting structure about a longitudinal axis of the subtalar joint, as seen in a top plan view thereof, for limiting motion of segments of the subtalar joint while yieldably resisting subtalar joint motion by way of providing resistance to the associated rotation of the tibia.
As explained more fully hereinafter, the subtalar joint either pronates or supinates about an oblique axis. The method of the invention further includes securing the supporting structure to the foot in a manner which applies a force to the foot in a direction which is orthogonal or nearly orthogonal to this oblique axis of the subtalar joint for effectively limiting motion thereof together with the supporting structure, especially in a direction to oppose supination of the subtalar joint in the preferred embodiments of the invention. The method of the invention can be performed with a shoe or an orthosis according to the invention, or with an orthosis of the invention in conjunction with a conventional shoe.
These and other objects, features and advantages of the present invention will become more apparent from a consideration of the following detailed description of disclosed embodiments of the invention and the accompanying drawings.